Before one could create a meaningful understanding of Descartes theory of knowledge, it is important one knows from the beginning the goal Descartes intended to achieve. Basically, Descartes’s works revolve around three goals.
The first was the quest for certainty. The conflicting opinions he found everywhere he went during his days were disheartening if not otiose.
The second goal was to fulfill the dream of a universal science. This goal, required him to find a unified set principles from which he could deduce all answers to scientific questions.
The last goal was reconciling the mechanistic view of the world found in science with human freedom and his own religious perspective.
According to Lawhead, the picture of the world as a deterministic physical machine threatened the uniqueness and freedom of the human soul and seemed to leave little room for God.
It was Descartes’ hope therefore to reconcile this tensions. The first two, he discussed in his theory of knowledge, that is, his epistemology. The third he espoused in his metaphysics. The epistemology and metaphysics of Descartes as seen also in all philosopher are in a relation of close interdependence. But while the latter often build the foundation for the former in most philosophies, the reverse is the case for Descartes. His epistemology leads to his metaphysics.
For Descartes to achieve his three main objectives, he felt philosophy and indeed knowledge had to be founded on a new foundation that will be indubitable. This need for a firm foundation, Descartes got from mathematics, especially Euclidean geometry in which first principles comprising definitions, postulates, and axioms serve as the foundation on which a superstructure of further propositions are based. It was his belief that from this Archimedean point, the rest of knowledge can be deduced the same way Euclid derive hundreds of theory from just ten foundation propositions. If a new foundation is sort, then there is need for a demolition of the previous shaky foundations like the architect that wants to build. While the bulldozer is the viable tool for the architect, the methodic doubt is the tool through which Descartes hope to arrive at such foundation.
The starting point for Descartes was to get a methodology through which he shall achieve this aim and he found the methodological doubting capable of fulfilling the goal. He therefore proceed to doubting all his previous beliefs until he got to a point he could no longer doubt the fact that he was doubting. Neither the deception of the senses hypothesis nor the possibility of a dream nor that of the existence an evil genius could fault the fact that he was doubting. The doubting thus shows that he equally exist, hence, “Corgito Ergo sum” (I think therefore I am) became the indubitable foundation on which all consequent knowledge can be based.
From this indubitable truth, Descartes went as far as not just giving the nature but also the existence of God. One question however remain unsolved, how does this foundation which Descartes thought he has found then validate other beliefs we have say in politics, arts and sciences?